1. Field of the Invention
This invention relates to vibratory material handling apparatus such as vibrating screens, feeders, conveyors and separators. More particularly, the invention pertains to a vibration exciter drive for a two mass vibratory system and to resilient elements for coupling the two masses.
2. Description of the Prior Art
A vibration exciter drive is shown in U.S. Pat. No. 3,703,236 and includes a fixed frequency drive motor shaft with a pulley mounted thereon, a rotary eccentric weight shaft with a pulley mounted thereon, and a drive belt trained about the pulleys. This drive is incorporated in a two mass vibratory system that includes a vibration exciter mounting having a rectangular tubular frame with elastomeric blocks positioned therein for supporting the vibration exciter. By variation of the number, sizes, placement or compression of the elastomeric blocks, the transmitted vibratory force component in the vertical and horizontal directions can be independently adjusted in order to obtain the desired vibratory motion in the vibrated structure and the desired natural frequency of vibration of the vibratory system.
A vibratory material handling apparatus with a rotating eccentric mass driver that is mounted on the apparatus by elastomeric bodies is shown in U.S. Pat. No. 3,583,553. The driver is driven by a fixed frequency motor mounted on the same shaft as the driver. Work producing vibrations are transmitted along an attack axis by compression of the elastomeric bodies while vibratory excursions other than in the direction of such attack axis are dissipated through flexure of the elastomeric bodies in shear. While the vibration exciter force is constant, changes in feed rate can result due to variations in the head load upon a pile of material to be vibrated.
In conventional two mass vibrating systems it is desirable to have a near resonance operation. Normally, it is not possible to change the operating frequency of the system and therefore it is necessary to change springs or weights after the system is assembled and operated. Variations in spring rates due to manufacturing tolerances and variations in trough weight due to both manufacturing tolerances and weight of material to be vibrated require adjustment of the natural frequency of the system for operation at a frequency near resonance level.